Copyright and Digitization
One of things Mr. Hirtle always makes clear is something we librarians at the Research Network try to make clear when we address one of your copyright, patent, trademark or similar questions, which is what he calls IANAL - I Am Not A Lawyer. For many of the issues, the issues are not black and white, which leads to litigation.
Librarians, as users of protected material, have a certain awareness of their obligations. One of the things I DID NOT KNOW is how digitization makes US, the librarians, the users. Whereas when someone goes to the library and uses the copier, or even uses the librarian as his or her agent, the patron is the user. So you'll be seeing some additional verbiage in the documents that we'll be sending to you.
Conversely, librarians and archivists have certain specific rights to copy copyrighted works through Section 108 of the Copyright Law as long as it's a single copy, and in the course of our jobs. Read about this in Circular 21.
There is also a notion in copyright law called "fair use". From the copyright page:
Section 107 also sets out four factors to be considered in determining whether or not a particular use is fair:
the purpose and character of the use, including whether such use is of commercial nature or is for nonprofit educational purposes;
the nature of the copyrighted work;
amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
the effect of the use upon the potential market for or value of the copyrighted work.
The distinction between "fair use" and infringement may be unclear and not easily defined. There is no specific number of words, lines, or notes that may safely be taken without permission. Acknowledging the source of the copyrighted material does not substitute for obtaining permission.
So the parameters are not at all clear. All factors must be weighed, though the courts have been particularly emphasizing the effect on the market. Here's a checklist that may help.